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| author | Ingo Molnar <mingo@elte.hu> | 2008-08-13 18:02:18 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-08-15 19:17:33 +0200 |
| commit | 2fdc86901d2ab30a12402b46238951d2a7891590 (patch) | |
| tree | 8f514c642a9b541ba474c68272c8a38104d8a1cd | |
| parent | 8d6ea9674cb12b90c800dc572214bf06f6ce8340 (diff) | |
| download | linux-2fdc86901d2ab30a12402b46238951d2a7891590.tar.gz linux-2fdc86901d2ab30a12402b46238951d2a7891590.tar.bz2 linux-2fdc86901d2ab30a12402b46238951d2a7891590.zip | |
x86: add MAP_STACK mmap flag
as per this discussion:
http://lkml.org/lkml/2008/8/12/423
Pardo reported that 64-bit threaded apps, if their stacks exceed the
combined size of ~4GB, slow down drastically in pthread_create() - because
glibc uses MAP_32BIT to allocate the stacks. The use of MAP_32BIT is
a legacy hack - to speed up context switching on certain early model
64-bit P4 CPUs.
So introduce a new flag to be used by glibc instead, to not constrain
64-bit apps like this.
glibc can switch to this new flag straight away - it will be ignored
by the kernel. If those old CPUs ever matter to anyone, support for
it can be implemented.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Ulrich Drepper <drepper@gmail.com>
| -rw-r--r-- | include/asm-x86/mman.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/asm-x86/mman.h b/include/asm-x86/mman.h index c1682b542daf..90bc4108a4fd 100644 --- a/include/asm-x86/mman.h +++ b/include/asm-x86/mman.h @@ -12,6 +12,7 @@ #define MAP_NORESERVE 0x4000 /* don't check for reservations */ #define MAP_POPULATE 0x8000 /* populate (prefault) pagetables */ #define MAP_NONBLOCK 0x10000 /* do not block on IO */ +#define MAP_STACK 0x20000 /* give out an address that is best suited for process/thread stacks */ #define MCL_CURRENT 1 /* lock all current mappings */ #define MCL_FUTURE 2 /* lock all future mappings */ |